Breakthrough with WDPre3

[bikerhifinut]

Hi Richard,
If that was meant for me, then unfortunately no. I haven't had any real chance to get out since the end of May.
I take it you refer to the Royal Enfield outfit?
Unfortunately I am "confined to barracks" along with Mrs Nut as she is very unwell and can not be left alone for any period of time, hopefully all to be resolved on Wednesday when she goes under the surgeons knife yet again.
Ok enough of my tribulations, things should get better after next week.

Andy.

[bikerhifinut]

For what its worth Richard, I can't see why you couldnt common the "earthy" side of the primary and secondary of the pre3 output transformer. You wouldnt get the galvanic isolation then but if you look at many power amp designs they have the secondary tied to earth as part of the feedback loop so I guess it should be ok???? And in any case the secondary could be grounded via the screen of the interconnect?

Andy.

[Richard]

Hi Andy, sorry to hear that. Coincidence then, perhaps not many of these up in your neck of the woods on a lovely day. I hope all goes well

[Richard]

Originally Posted by bikerhifinut

For what its worth Richard, I can't see why you couldnt common the "earthy" side of the primary and secondary of the pre3 output transformer. You wouldnt get the galvanic isolation then but if you look at many power amp designs they have the secondary tied to earth as part of the feedback loop so I guess it should be ok???? And in any case the secondary could be grounded via the screen of the interconnect?

Andy.

Hi Andy, Well, back on topic,
Pre3 primary is connected to the HT so we wouldn't connect that to the secondary, but, as you say about power amps, I can't see a reason not to connect the secondary to Pre3 ground (and thereby grounding the Quad input).
As you also point out it would be usual for it to be connected to ground via the power amp signal ground - and that is my train of thought for non-earthed amps like the Quad QSP - they are not connected to ground either signal to signal or via the mains so when they are connected to Pre3 their input is floating,

[bikerhifinut]

Richard,

Of course you are right I hadnt thought that one through had I?
It does start to make sense now.
The power amp isn't grounded so any stray emf's or potential differences between the "Earthy side" of pre out and power in wouldnt be "sunk" to 0V?
I'd say give it a go, take it to the signal ground rather than case or mains earth and see what happens, It cant do any electrical harm that I can see, maybe use a "Bullet" connector so the link can be broken or more elegantly an "Earth lift" switch as seen on some equipment.
That Royal Enfield is an older variant of mine with a "Pre-Unit construction" engine, i.e. motor and gearbox are separate entities, its Fairly modern as evidenced by the disc brake and Indicators. The sidecar is however Identical and could well have been fitted at Watsonian-Squire as they were the Royal Enfield Importers until last year.
Andy

[bob orbell]

Originally Posted by bikerhifinut

Hi Richard,
If that was meant for me, then unfortunately no. I haven't had any real chance to get out since the end of May.
I take it you refer to the Royal Enfield outfit?
Unfortunately I am "confined to barracks" along with Mrs Nut as she is very unwell and can not be left alone for any period of time, hopefully all to be resolved on Wednesday when she goes under the surgeons knife yet again.
Ok enough of my tribulations, things should get better after next week.

Andy.

Sorry to hear about Mrs Nut Andy, please let us know if all goes to plan. BOB